National Instruments 321645c-01 Manual Do Utilizador

Chapter 2

Function Reference — GPCTR_Control

NI-DAQ FRM for PC Compatibles

2-212

©

 National Instruments Corporation

You need to use this function with action = 

ND_PROGRAM

 

PROGRAM

 after completing the 

configuration sequence consisting of calling 

GPCTR_Set_Application

 followed by 

optional calls to 

GPCTR_Change_Parameter

 and 

GPCTR_Config_Buffer

.

Use the 

ND_PREPARE

 and 

ND_ARM

 actions to program the counter before arming. You might 

find this useful if it is critical to minimize time between a software event (a call to 

GPCTR_Control

) and a hardware action (counter starts counting).

You can use this function with action = 

ND_RESET

 when you want to halt the operation the 

general-purpose counter is performing.

Use actions 

ND_COUNT_UP

 and 

ND_COUNT_DOWN

 to change the counting direction. 

You can do this only when your application is 

ND_SIMPLE_EVENT_CNT

 or 

ND_BUFFERED_EVENT_CNT

 and the counter is configured for software control of the 

counting direction for UP or DOWN.

For 6602 and 455X devices only, use action 

ND_SWITCH_CYCLE

 only if your application is 

ND_PULSE_TRAIN_GNR

.

ND_DISARM

Disarm the general-purpose counter

ND_PROGRAM

ND_PREPARE

 and then 

ND_ARM

 the counter

ND_RESET

Reset the general-purpose counter

ND_COUNT_UP

Change the counting direction to UP. See 

 

below.

ND_COUNT_DOWN

Change the counting direction to DOWN. See 

 below.

ND_SWITCH_CYCLE

(6602 and 455X 
devices only)

This action can be used to change the properties of a continuous 
pulse that was started using 

GPCTR_Set_Application

 with 

application = 

ND_PULSE_TRAIN_GNR

. If you use 

ND_SWITCH_CYCLE

 after the counter is armed, the counter 

will be reloaded with the latest values specified by 

GPCTR_Change_Parameter

 with paramID = 

ND_COUNT_1

 

and 

ND_COUNT_2

.

Table 2-30.  Legal Values for the action Parameter (Continued)